In general, channels of a mobile communication system include downlink channels for transmitting data from a base station to user equipments and uplink channels for transmitting data from user equipments (UE) to a base station (Node-B). A mobile communication system based on high-speed packet access (HSPA) technology enabling high-speed packet data services includes a dedicated physical data channel (DPDCH) and a dedicated physical control channel (DPCCH) to transmit high-speed packet data. In the HSPA mobile communication system, uplink channels for high-speed packet transmission from a user equipment to a base station include a high speed dedicated physical control channel (HS-DPCCH), dedicated physical control channel (DPCCH) and dedicated physical data channel (DPDCH), and further include an enhanced dedicated physical control channel (E-DPCCH) and enhanced dedicated physical data channel (E-DPDCH).
The data rate for packet data over E-DPDCH (an uplink high-speed packet data channel) is determined in consideration of the remaining power in the user equipment. FIG. 1 illustrates uplink physical channels and the total power available to a user equipment, and FIG. 2 depicts the relationship between the remaining power of the user equipment and the packet data rate. FIG. 2 indicates that the uplink packet data rate of a user equipment is proportional to the amount of power allocated to an uplink packet data channel E-DPDCH. However, as indicated by FIG. 1, power allocatable to the uplink packet data channel E-DPDCH is limited to the remaining power after power is allocated to all uplink physical channels other than E-DPDCH.
As described above, only the remaining power after power allocation to all uplink physical channels other than E-DPDCH is available to E-DPDCH. However, when a high data rate is required for data upload (as in the case of high order modulation), it is preferable to allocate as much transmit power to E-DPDCH as possible.